1. Field of the Invention
Exemplary embodiments relate to turbo processing and transmitting a digital broadcasting transport stream, a digital broadcasting transmission and reception system, and a method of processing signals thereof, and more particularly, to turbo processing, transmitting and receiving a digital broadcasting transport stream to enhance reception performance of a terrestrial-wave digital television (DTV) system in the U.S. in accordance with the Advanced Television Systems Committee (ATSC) vestigial sideband (VSB) transmission system through information exchange and mapping with respect to a dual transport stream (TS) which includes normal data and turbo data, and a digital broadcasting transmission and reception system.
2. Description of the Related Art
The Advanced Television Systems Committee (ATSC) vestigial sideband (VSB) transmission system, which is used in a terrestrial-wave digital television (DTV) system in the U.S., is a single-carrier system that transmits one field synchronization (sync) segment for each unit of 312 data segments. Therefore, reception performance of the ATSC VSB system is inferior over weak channels, especially over a Doppler-fading channel.
FIG. 1 is a block diagram of an ATSC VSB digital broadcasting transceiver of the related art. The digital broadcasting transceiver shown in FIG. 1 is configured in accordance with an enhanced VSB (E-VSB) system proposed by Phillips, and produces and transmits a dual stream configured by adding enhanced or robust data to normal data of the standard ATSC VSB system.
As shown in FIG. 1, a digital broadcasting transmitter includes a randomizer 11, a Reed-Solomon (RS) encoder 12 having a concatenated encoder form adding parity bytes to a dual transport stream to enable errors generated by channel impairments during transmission to be corrected during reception, an interleaver 13 interleaving the RS-encoded data according to a predetermined pattern, and a 2/3 rate trellis encoder 14 performing trellis-encoding at a rate of 2/3 with respect to the interleaved data and mapping the interleaved data to 8-level symbols. With this structure, the digital broadcasting transmitter performs error-correction encoding with respect to the dual stream.
The digital broadcasting transmitter further includes a multiplexer 15 inserting field synchronization (sync) and segment sync in the error-correction encoded data according to a data format shown in FIG. 2, and a modulator 16 inserting a pilot by adding a predetermined direct current (DC) value to the data symbols and the inserted segment sync and field sync, amplitude-modulating the resulting signal onto an intermediate frequency (IF) carrier, filtering the resulting IF signal to produce a vestigial sideband (VSB) signal, up-converting the VSB signal to a radio-frequency (RF) signal having a frequency of a desired channel, and transmitting the RF signal through the channel.
Accordingly, in the digital broadcasting transmitter, the normal data and the enhanced or robust data are multiplexed according to the dual stream system that transmits the normal data and the enhanced or robust data on one channel and are inputted to the randomizer 11. The inputted data is randomized by the randomizer 11, and the randomized data is outer-encoded by the RS encoder 12 which is an outer encoder. The interleaver 13 distributes the encoded data according to the predetermined pattern. The interleaved data is inner-encoded by the trellis encoder 14 in 12-symbol units. The inner-encoded data is mapped to 8-level symbols. The field sync and the segment sync are inserted in the mapped data. The pilot is inserted and the VSB modulation is performed. The VSB signal is up-converted to the RF signal, and the RF signal is transmitted through the channel.
A digital broadcasting receiver shown in FIG. 1 includes a tuner (not shown) converting the RF signal received through the channel to a baseband signal, a demodulator 21 performing synchronization detection and demodulation with respect to the baseband signal, an equalizer 22 compensating for channel distortion generated by multiple transmission paths with respect to the demodulated signal, a Viterbi decoder 23 correcting errors of the equalized signal and decoding the error-corrected signal to symbol data, a deinterleaver 24 rearranging the symbol data according to the predetermined pattern by which data was distributed by the interleaver 13 of the digital broadcasting transmitter, an RS decoder 25 correcting errors, and a derandomizer 26 derandomizing the data corrected by the RS decoder 25 and outputting an MPEG-2 (Moving Picture Experts Group) transport stream. Therefore, the digital broadcasting receiver of FIG. 1 down-converts the RF signal to the baseband signal in a reverse order relative to the digital broadcasting transmitter, demodulates and equalizes the converted signal, and performs channel-decoding, thereby recovering the original signal.
FIG. 2 shows a VSB data frame where the segment sync and the field sync are inserted according to an 8-VSB system which is used in the DTV system in the U.S. As shown in FIG. 2, one frame includes two fields. One field includes one field sync segment which is a first segment of the field, and 312 data segments. In the VSB data frame, one segment corresponding to one MPEG-2 packet comprises a 4-symbol segment sync and 828 data symbols. The segment sync and the field sync in FIG. 2 are used for synchronization and equalization in the digital broadcasting receiver. More specifically, the segment sync and the field sync, which are known to the digital broadcasting transmitter and receiver, are used as reference signals when the receiver performs synchronization and equalization. The U.S. terrestrial-wave digital broadcasting system of FIG. 1 is configured to produce and transmit the dual stream by adding the enhanced or robust data to the normal data of the ATSC VSB system of the related art. Therefore, the U.S. terrestrial-wave digital broadcasting system transmits the enhanced or robust data as well as the normal data.
Although the enhanced or robust data is transmitted in the dual stream in addition to the normal data, inferior reception performance due to multipath channel distortion caused by transmission of the normal data stream is not remarkably improved. In fact, almost no improvement in the reception performance is obtained by the improved normal data stream. Moreover, reception performance is not much improved with respect to the enhanced or robust stream, either.